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go back on不守,不履行,违背
2.A State Department spokesman said it was too early to say whether or not the victims had been deliberately targeted.
whether or not是否
例句：I am deliberating whether or not to buy a new car.
我在考虑是否要买一辆新汽车。
whether可以和not连用而if不可以。
3.Now scholars for their British Shakespeare publisher, Arden, say they believe the work was written by the playwright who died in 1616, in collaboration with another dramatist John Fletcher.
in collaboration with与…合作
例句：He wrote the book in collaboration with his colleagues.
他与同事合作写了这本书。
4.Beckham's current on loan to AC Milan from Los Angeles Galaxy.
on loan出借,借出
例句：All of these Books are on loan from the main library.
这所有的书都是自总馆借来的。
